1. Field of the Invention
Embodiments of the present invention generally relate to processing a moving substrate in a plasma environment.
2. Description of the Related Art
In the manufacture of integrated circuits and other electronic devices, plasma processes are often used for deposition or etching of various material layers. Plasma processing offers many advantages over thermal processing. For example, plasma enhanced chemical vapor deposition (PECVD) allows deposition processes to be performed at lower temperatures and at higher deposition rates than achievable in analogous thermal processes. Thus, PECVD is advantageous for integrated circuit and flat panel display fabrication with stringent thermal budgets, such as for very large scale or ultra-large scale integrated circuit (VLSI or ULSI) device fabrication.
One problem that has been encountered with plasma processing in integrated circuit fabrication is that devices may become damaged as a result of exposure to non-uniform plasma conditions, such as electric field gradients. For example, RF power in-rush occurring during plasma ignition may result in non-uniform plasma generation and distribution in the process region. The susceptibility or degree of device damage depends on the stage of device fabrication and the specific device design. For example, a substrate having a relatively large antenna ratio (e.g., area of metal interconnect to gate area) is more susceptible to arcing during plasma ignition than a substrate having a smaller antenna ratio. The substrate having a relatively large antenna ratio also tends to collect charges and amplify the charging effect, thereby increasing the susceptibility to plasma damage, such as arcing to the device being formed on the substrate. Devices containing an insulating or dielectric layer deposited on a substrate are susceptible to damage due to charges and/or potential gradients accumulating on the surface of the dielectric layer.
Additionally, the accumulation of charges or buildup of electrical gradients on the substrate may cause destructive currents to be induced in portions of the metalized material. The induced current often results in arcing between dielectric layers and/or to the processing environment (e.g., a system component). Arcing may not only lead to device failure and low product yield, but may also damage components of the processing system, thereby shortening the useful life of system components. The damaged system components may cause process variation or contribute to particle generation, both of which may further reduce product yield. As the feature size of devices becomes smaller and dielectric layers become thinner, prevention of unstable and/or non-uniform plasma distribution becomes increasingly important not only for ensuring device electrical performance and product yield, but also for extending the service life of system components and managing system operating costs.
Therefore, there is a need for an improved method and apparatus for plasma processing.